Nomura’s capitalization had benefited from a cost-reduction program and lower holdings of illiquid assets, the agency said.

The move follows the ratings company’s two downgrades of Nomura since 2009, when securities firms worldwide were roiled by the global financial crisis. Chief Executive Officer Koji Nagai has pared expenses and overseen a profit resurgence since he took the post in August 2012, although earnings growth has stalled this year as waning demand for Japanese stocks erodes brokerage commissions.